1. Field of the Invention
The present invention relates generally to a noise filter of a CR type or an LCR type, and more particularly, to an improvement of a noise filter in which at least one resistance film is formed on the outer surface of a dielectric body to constitute a resistance element or resistance elements.
2. Description of the Prior Art
FIG. 5 is a perspective view showing one example of a conventionally known noise filter. A noise filter 1 has a structure in which a winding 3 is wound around a core of a bobbin 2 composed of dielectric ceramics to constitute a coil portion 4. The bobbin 2 has a structure in which a pair of collar portions 5 and 6 is formed in both ends of the core, and electrodes 6a to 6c are formed spaced apart from each other by a predetermined distance on the outer major surface of the collar portion 5.
One end 3a and the other end 3b of the winding 3 constituting the above described coil portion 4 are electrically connected to the electrode 6a and the electrode 6c, respectively. The electrode 6b is formed as an earth electrode so as to take out capacitance between the electrode 6a and the electrode 6c in the bobbin 2 composed of dielectric ceramics. Consequently, an equivalent circuit of the noise filter 1 is as shown in FIG. 6. The electrodes 6a to 6c are used as terminals for connection to the exterior, thereby to construct a noise filter of a .pi. type.
When the above described noise filter 1 is used with it being inserted into a signal line, however, a signal waveform is distorted by the insertion of the noise filter 1, although a target noise can be reduced, to produce a new noise.